PM-728VT Questions after two-years use

[Bryanaverill]

If you are not able to measure your quill OD, you can send the quill in and we can check it for you if needed.

Its a fine line between play or flex, I would call "play" like where you barely touch it and it bumps back and forth. Almost like one finger hardly any pressure kind of thing, if that makes sense.

The "flex" on the other hand would be a little different, that's going to happen. I can move the head .005 or so on our large CNC machining centers by pushing on them. They don't have a quill though so not quite the same thing, there is no moving/sliding part to have play, this would be all flex. And the quill lock did make a difference on yours too

I just measured a couple quills, they are both right around 2.361" (plus or minus .0002) (Just under 60mm if going by Metric) See where you are with yours. The quill bore is 60mm on these mills.

If any issues, please email our tech@precisionmatthews.com I am not on here enough to reply fast (Please put a copy of this in so they know what you are talking about)

Thank you for joining the conversation. I took a few measurements:
1) Quill diameter 2.3610"±.0001. I took several measurements and the quill appears to be cylindrical.
2) Radial quill movement with indicator mounted to head: .002".
3) Radial spindle movement, minus quill: .001".
4) Total radial movement from table to spindle (quill+spindle+column deflection): .004".

I was putting about 5 pound of radial force into the spindle when taking measurements.

At this point, I think this is typical for a machine of this type. Perhaps a finer fitting quill and better spindle bearings would help, but that seems like a lot of work and uncertainty that it would accomplish an improvement. I have adjusted my hole spotting process and I'm getting good results. A little more time consuming but not a huge deal.

Thanks
Bryan

 

[compact8]

I have exactly the same problem with my 30-year old ( but not used much ), Austrian-made EMCO FB2 bench mill which weights 30% less compared with the PM728VT , https://www.hobby-machinist.com/threads/quill-tilt.113862/

I guess this is a rather common problem for mills of this class ?

 

[wrmiller]

My old PM25 (Weiss) mill was given back to me this year by a good friend. I don't think he intentionally abused it (serious newbe), but it has serious wear in the spindle and quill splines as well as wear in the head bore and quill interface.

Now, there is a small chance that I may be able to purchase a small (read lower cost) mill next year, so I have been looking over my choices on the PM site. Unfortunately, I got spoiled by my PM935 I had: Hardened and ground ways/table. Ground quill and bore, with hard chromed quill, oiling system, etc., etc..

None of that exists on the bench mill class machines. (Taiwan bench mills have one-shot oiling, but non-hardened ways)

I suspect that any of these mills, given even a couple of years of even just weekend project use, will show significant wear. Machines with higher quality castings will fair better than those machines with typical soft-iron castings, but at some point even these machines will become not so accurate. Lower cost machines are just not as good as the higher cost (and higher quality) machines. Maybe I will have to sell a kidney? (just kidding...) LOL...

 

[davidpbest]

Here is what it looks like on the PM-935 baby knee mill:

https://flic.kr/p/2jto783

 

[compact8]

Here is what it looks like on the PM-935 baby knee mill:

https://flic.kr/p/2jto783

This is showing the head flexing or quill play ?

 

[davidpbest]

This is showing the head flexing or quill play ?

as I said in the video, head play. If you want to see what the spindle looks like, let me know. I have that video too.

 

[davidpbest]

Here are the quill rigidity checks for the PM-935: https://www.flickr.com/gp/davidpbest/N6D3M4777L

 

[compact8]

Here are the quill rigidity checks for the PM-935: https://www.flickr.com/gp/davidpbest/N6D3M4777L

Sorry….. I have turned off the audio. Yes, it will be very intersting to see the spindle play and how it compares with that of my humble bench mill.

 

[compact8]

Here are the quill rigidity checks for the PM-935: https://www.flickr.com/gp/davidpbest/N6D3M4777L

Thanks for sharing the video. If I have understood it correctly, the quill is locked in the test. I believe this is not quite the quill play problem described by the OP and experienced by myself. In my case the quill is unlocked. When the quill is lowered by operating the feed handle, it will tilt and the XY of the tool tip will change.

This brings two problems : 1) the XY of drilled holes are inaccurate and 2) the holes are not perpendicular to the table. The hole diameter seems to be unaffected though.

 

[davidpbest]

Thanks for sharing the video. If I have understood it correctly, the quill is locked in the test. I believe this is not quite the quill play problem described by the OP and experienced by myself. In my case the quill is unlocked. When the quill feed handle is pressed and the quill lowered, it will tilt and the XY of the tool tip will change.

This brings two problems : 1) the XY of drilled holes are inaccurate and 2) the holes are not perpendicular to the table.

My PM-935 quill does not shift laterally when it is lowered under power and load like a drill or a boring bar or end mill. Neither does the quill on my 20 year old Rong Fu 45 (original) with 200,000 miles on it. On my 935, there is a brass shim that surrounds the OD of the quill and is sandwiched between the quill cassette and the cast head housing. It's called out in the parts explosion diagram in the back of the user manual as a "quill skirt". I don't see anything like this called out on the 728.